Some of them - yes, some others not. There is some gluing magic in place which has to be written for every C++ function and class in order to make them visible on the perl side.

To get an overview of what is already available from the interactive shell and scripts, you can browse the interactive help system. For example, change to application "graph" and enter help "functions/ or help "objects/ then use TAB completion to see the proposals. Or look at the release documentation at https://polymake.org/release_docs/latest/graph.html, it contains the same information.